This invention relates to a smooth muscle growth inhibitory composition comprising apM1 (adipose most abundant gene transcript 1) as an active ingredient, a method for diagnosis of arteriosclerosis (atherosclerosis) which comprises assaying said apM1 in a sample, and a diagnostic kit for arteriosclerosis which comprises an antibody against said apM1 as an active component.
It is well known that, in modern society, obesity or an excessive accumulation of body fat is involved in the development of diabetes mellitus, hyperlipidemia, hypertension, and atherosclerotic diseases inclusive of angina pectoris and myocardial infarction. With obesity, not only genetic factors but also environmental factors are associated.
Recently, leptin and many other obesity-related genes have been isolated from animal models. While the group of these genes thus isolated is suspected to be involved in the establishment of obesity in man, various environmental factors such as the excessive food intake and insufficient physical exercise by contemporary man are also considered to be playing a crucial role in the development of diabetes mellitus and atherosclerosis via fat storage.
Not only the search for obesity-related genes but also the approach toward elucidation of the specific genes expressed in adipose tissues under overnutrition and of the influences of such gene transcripts on the individual seem to be of remarkable significance for expatiation of the etiologies of said diseases and establishment of relevant therapeutic modalities.
The object of this invention is to cast light on the obesity-related genes and their expression products which should be useful for elucidation of the pathogenesis of various obesity-related diseases, particularly atherosclerotic diseases such as angina pectoris, myocardial infarction, etc., and establishment of pertinent therapeutic modalities and to establish therapeutic and diagnostic methods for the diseases by utilizing such genes and expression products.
The inventors have conducted intensive studies for accomplishing the above object and made it clear previously that accumulation of fat, particularly visceral fat in the abdominal cavity, is closely associated with abnormal glucose tolerance, hyperlipidemia and hypertension. Furthermore, through large-scale sequencing analyses of the genes expressed in adipose tissue, they elucidated that many secretory protein genes have been expressed in adipose tissue and that, particularly in visceral fat, the expression of various bioactive substance genes can be observed. In addition to the cloning of those known genes, the inventors succeeded in cloning an adipose tissue-specific collagen-like protein apM1 gene [Biochem. Biophys. Res. Commun., 221, 286-289 (1996)].
This apM1 gene was found to be coding for the secretory protein (apM1) consisting of 244 amino acid residues, contain a 66-residue collagen-like motif (G-X-Y), and have homology with the Clq subcomponent of the complement system and collagen X and VII. However, the physiological function of this gene and its expression product apM1 remained to be known.
In the ensuring research, the inventors made a series of investigations in regard to the expression of said apM1 gene by the genetic engineering technique, preparation of an antibody against the expression product apM1, establishment of an apM1 assay system utilizing said antibody, and relationship of the blood apM1 concentration determined by using said assay system to the body fat distribution or various diseases. The research led to the novel finding, inter alia, that apM1 has smooth muscle growth inhibitory activity and that the blood apM1 concentration faithfully reflects the atherosclerotic change.
Furthermore, the inventors obtained the novel finding that apM1 is effective in the prevention and treatment of post-angioplasty restenoses, such as restenosis after percutaneous transluminal coronary angioplasty (PTCA) using a stent, and for that matter, in the prophylaxis and therapy of atherosclerotic diseases accompanied by angiopathy, such as angina pectoris and myocardial infarction. This invention has been developed on the basis of the above finding.
In accordance with the invention, there is provided a smooth muscle growth inhibitory composition comprising a pharmacologically effective amount of at least one member selected from the group consisting of apM1 and its salt in combination with a pharmaceutically acceptable carrier.
Furthermore, in accordance with the invention, there is provided a therapeutic and prophylactic composition for post-angioplasty restenoses which comprises a pharmacologically effective amount of at least one member selected from the group consisting of apM1 and its salt in combination with a pharmaceutically acceptable carrier.
There is also provided in accordance with the invention a prophylactic and therapeutic composition for arteriosclerosis which comprises a pharmacologically effective amount of at least one member selected from the group consisting of apM1 and its salt in combination with a pharmaceutically acceptable carrier.
There is also provided in accordance with the invention a method for diagnosis of arteriosclerosis which comprises quantitating apM1 in a sample with an anti-apM1 antibody and comparing the value thus found with the values measured in healthy subjects and in patients with arteriosclerosis.
In addition, the present invention provides a diagnostic kit for arteriosclerosis, which comprises an anti-apM1 antibody as an active component, and a monoclonal anti-apM1 antibody which is effective in diagnosing the arteriosclerosis.
The smooth muscle growth inhibitory composition according to the invention is effective, through its smooth muscle growth inhibitory activity, in the prophylaxis and therapy of atherosclerotic diseases accompanied by angiopathy, such as angina pectoris, myocardial infarction inclusive of thrombosis, brain infarction, etc. and in the arrest of progression of such atherosclerotic diseases. In fact, apM1 as the active ingredient of the composition of the invention has an ability to inhibit expression of the cell adhesion molecules governing the onset of arteriosclerosis, namely VCAM-1 (vascular cell adhesion molecule-1), ELAM (endothelial leukocyte adhesion molecule), ICAM-1 (intercellular adhesion molecule-1), and so on. It is because of this action that the composition of the invention antagonizes the onset of various atherosclerotic diseases.
Consequently, the invention further provides a pharmaceutical composition for inhibiting the expression of adhesion molecules in vascular endothelial cells.
The fact that apM1 inhibits expression of said cell adhesion molecules indicates that the composition of the invention can be indicated for the prophylaxis and therapy of bronchial asthma which is a disease related to type I allergy accompanying eosinophilic infiltration and also known to be a disease associated with an enhanced expression of VCAM-1, for instance.
Furthermore, in view of the fact that said ICAM-1 and ELAM are known to be inflammation-related adhesion molecules, the composition of the invention comprising apM1 as an active ingredient may be indicated as an antiinflammatory agent or a therapeutic drug for rheumatoid arthritis, for instance, by taking advantage of said inhibitory effect on the expression of adhesion molecules.
Furthermore, the composition of the invention is effective in the prevention and treatment of post-angioplasty restenoses, for example in stent PTCA cases. Thus, after an operation for neovascularization against the coronary artery stenosis in angina pectoris or myocardial infarction, the post-ischemic reperfusion and injury of vascular endothelial cells evoke expression of adhesion molecules in vascular endothelial cells and consequent proliferation of smooth muscle cells to induce a restenosis. The composition of the invention inhibits such expression of adhesion molecules and growth of smooth muscle cells to thereby contribute to the prevention of ischemic restenoses after angioplasty.
The method for diagnosis of arteriosclerosis according to the invention utilizes a new marker, that is smooth muscle growth potency (DNA-synthesizing ability of smooth muscle cells). The diagnosis method of the invention is carried out by determining and quantitating the apM1 level in a sample with a specific antibody against apM1.
The production of apM1 for use as the active ingredient of the composition of the invention, preparation of the composition using apM1 as an active ingredient, production of an antibody against apM1, and assay of apM1 are now described in sequence.
The designation of amino acids, peptides, nucleotide sequences, nucleic acids, etc. by abbreviations in this specification is in conformity with the rules of nomenclature recommended by IUPAC-IUB (IUPAC-IUB Communication on Biological Nomenclature, Eur. J. Biochem., 138, 9(1984)), xe2x80x9cThe Guidelines for Drafting of Specifications Etc. Containing Nucleotide Sequence or Amino Acid Sequence Informationxe2x80x9d (Edited by the Japanese Patent Office, June, 1998) and the conventions in the relevant field of art.
apM1 can be provided in the form of a recombinant protein by the established genetic engineering techniques [e.g. Science, 224, 1431(1984): Biochem. Biophys. Res. Comm., 130, 692(1985); Proc. Natl. Acad. Sci., USA., 80, 5990 (1983)]. In this case, as the apM1 gene, the gene which was previously established by the present inventors can be used [Biochem. Biophys. Res. Commun., 221, 286-289 (1996)].
As an alternative, apM1 can be produced by the conventional method for chemical synthesis in accordance with the information on the amino acid sequence encoded by said gene.
More particularly, the production of apM1 by a genetic engineering technique comprises constructing a recombinant DNA with which the gene coding for the objective protein may be expressed in a host cell, introducing the DNA into the host cell to obtain a transformant and culturing the transformant.
As the host cell mentioned above, cells derived from eucaryotes and prokaryotes can be employed. The eucaryotic cell includes cells of vertebrates and cells of eucaryotic microorganisms. As the cell of a vertebrate, the monkey cell line COS [Cell, 23, 175 (1981)], the Chinese hamster ovarian cell line and the corresponding dihydrofolate reductase-deficient cell line [Proc. Natl. Acad. Sci., USA., 77, 4216 (1980)] and the like are frequently used but these are not exclusive choices.
As the expression vector of a vertebrate origin, a vector having a promoter sequence located upstream of the gene to be expressed, RNA (precursor) splice site, a polyadenylation site and a transcription terminating sequence, among others, can be generally used. Where necessary, the vector may further have a replication origin. As an example of such expression vector, pSV2dhfr harboring an early promoter of SV40 can be mentioned (Mol. Cell. Biol., 1, 854 (1981)).
As the eucaryotic microorganisms, yeasts are generally used and, among them, yeasts of the genus Saccharomyces can be used with advantage. As the expression vector derived from a eucaryotic microorganism such as a yeast, pAM82 having a promoter for the acidphosphatase gene [Proc. Natl. Acad. Sci., USA., 80, 1 (1983)], among others, can be utilized.
As the prokaryotic host, Escherichia coli and Bacillus subtilis are generally used most frequently. When they are used as hosts, it is advantageous to select a plasmid vector which can be replicated in the host microorganism and in order that the objective gene may be expressed in the vector, use an expression plasmid provided with a promoter region and an SD (Shine-Dalgano) sequence upstream of the gene and, further, with an initiation codon (e.g. ATG) required for the start of protein synthesis. As said Escherichia coli as the host, E. coli K12 is generally used, and as the vector, pBR322 or its modification product is generally used. However, these are not exclusive choices but the various known bacterial strains and vectors can likewise be employed. Examples of the promoter that can be used are tryptophan (trp) promoter, lpp promoter, lac promoter, and PL/PR promoter.
Introduction of the resulting recombinant DNA into the host cell for transformation can be carried out in the routine manner.
The transformant obtained can be cultivated by the conventional manner, whereby the objective recombinant protein is expressed, produced, and accumulated or secreted intracellularly, extracellularly or on the cell membrane. The medium for the cultivation can suitably be selected from among various media in routine use according to the host cell selected. The cultivation of the transformant can also be carried out under conditions suited to the particular host cell.
Where necessary, the apM1 obtained in the above manner can be isolated and purified by various separation procedures utilizing the physical, chemical and other characteristics thereof [Biochemical Data Book II, 1175-1259, First Edition, 1st impression, Jun. 23, 1980, published by Tokyo Kagaku Dojin, K.K.; Biochemistry, 25 (25), 8274 (1986); Eur. J. Biochem., 163, 313 (1987), etc.]. More particularly, said isolation and purification can be achieved by the conventional reconstitution treatment, treatment with a protein-precipitating (salting-out) agent, centrifugation, osmotic pressure shock method, sonication, ultrafiltration, various types of liquid chromatography such as molecular sieve chromatography (gel filtration), adsorption chromatography, ion-exchange chromatography, affinity chromatography, high-performance liquid chromatography (HPLC), etc., dialysis, and soon, as used either singly or in combination.
Alternatively, the apM1 mentioned above can also be produced by the general method for chemical synthesis based on the amino acid sequence information. The method includes the conventional liquid-phase and solid-phase methods for peptide synthesis. In more detail, each of these methods includes the so-called stepwise elongation technique which comprises condensing component amino acids one after another for chain extension according to the amino acid sequence information, and the fragment condensation technique which comprises synthesizing fragment peptides each consisting of several amino acid residues in advance and coupling them together one after another according to said information.
The condensation reaction for use in the above method of peptide synthesis can also be carried out in the conventional manner. For example, the method which can be used includes the azide method, mixed acid anhydride method, DCC method, activated ester method, redox method, DPPA (diphenylphosphoryl azide) method, DCC+ additive (e.g. 1-hydroxybenzotriazole, N-hydroxysuccinimide, or N-hydroxy-5-norbornene-2,3-dicarboximide) method, and Woodward""s method, among others.
The solvent that can be used in those methods can also suitably be selected from among those solvents which are well known to be of use in peptide-forming condensation reactions. As specific examples, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), hexaphosphoramide, dioxane, tetrahydrofuran (THF), ethyl acetate, etc., inclusive of mixtures thereof, can be mentioned.
In conducting the peptide synthesis reactions, the carboxyl groups of amino acids or peptides which are not to be involved in the respective reactions can be protected generally by esterification, e.g. in the form of a lower alkyl ester, e.g. methyl ester, ethyl ester or tert-butyl ester, or an aralkyl ester, e.g. benzyl ester, p-methoxybenzyl ester or p-nitrobenzyl ester.
Amino acids having a functional group in the side chain, for example the hydroxyl group of a tyrosine residue, may be protected with acetyl, benzyl, benzyloxycarbonyl, tert-butyl or the like, although such protection is not necessarily indispensable.
Moreover, the guanidino group of an arginine residue, for instance, can be protected with a suitable protective group such as nitro, tosyl, p-methoxybenzenesulfonyl, methylene-2-sulfonyl, benzyloxycarbonyl, isobornyloxycarbonyl or adamantyloxycarbonyl.
The reactions for elimination of such protective groups from the protected amino acids or peptides, or from the final protein, can also be carried out by the conventional procedures, for example by the catalytic reduction method or by the method using liquid ammonia/sodium metal, hydrogen fluoride, hydrogen bromide, hydrogen chloride, trifluoroacetic acid, acetic acid, formic acid, or methanesulfonic acid.
The apM1 thus obtained can be purified by the various procedures mentioned hereinbefore, for example the procedures in routine use in peptide chemistry, such as ion exchange chromatography, partition chromatography, gel permeation chromatography, counter-current distribution, and so forth.
The composition of the invention comprises apM1 or a pharmacologically acceptable salt thereof as an active ingredient. The salt includes those with alkali metals, alkaline earth metals and ammonium, such as the sodium, potassium, lithium, calcium, magnesium, barium and ammonium salts. These salts can be produced by the methods well known in the art. The above-mentioned salt further includes acid addition salts which can be prepared by reacting apM1 with a suitable organic or inorganic acid in the per se known manner. Examples of the acid addition salts are hydrochloride, hydrobromide, sulfate, bisulfate, acetate, oxalate, valerate, oleate, laurate, borate, benzoate, lactate, phosphate, p-toluenesulfonate (tosylate), citrate, maleate, fumarate, succinate, tartrate, sulfonate, glycolate, ascorbate, benzenesulfonate, napsylate and like salts.
The composition according to the invention is generally provided and put to use in the form of a pharmaceutical preparation containing a pharmacologically effective amount of said active ingredient together with a suitable pharmaceutical carrier.
The carrier that can be utilized in such a pharmaceutical preparation includes various diluents and/or excipients, such as fillers, volume builders, binders, humectants, disintegrators, surfactants, lubricants, and the like. These carriers are conventionally used according to the desired unit dosage form.
The unit dosage forms of the pharmaceutical preparation can be selected from a broad variety according to the therapeutic objectives. Typical examples include solid forms such as tablets, pills, powders, fine powders, granules and capsules, and liquid forms such as a solution, a suspension, an emulsion, syrup and an elixir. These preparations are classified, by route of administration, into oral preparations, parenteral preparations, transnasal preparations, vaginal preparations, rectal suppositories, sublingual tablets, ointments, and the like, and each can be formulated and molded or otherwise processed by the established pharmaceutical procedure. Furthermore, such pharmaceutical preparations may be supplemented with various additives which can be formulated in ordinary pharmaceutical preparations, such as the stabilizer, antibacterial agent, buffer, isotonizing agent, chelating agent, pH control agent and surfactant, each at a suitable level.
The stabilizer includes human serum albumin and those L-amino acids, carbohydrates and cellulose derivatives which are conventionally used. These can be used each alone or in combination with a surfactant or the like. Particularly, such a combination may contribute to an enhanced stability of the active ingredient.
The L-amino acids are not particularly restricted but include glycine, cysteine, glutamic acid and so on.
The carbohydrates are not particularly restricted but include monosaccharides such as glucose, mannose, galactose and fructose; sugar alcohols such as mannitol, inositol and xylitol; disaccharides such as sucrose, maltose and lactose; and polysaccharides such as dextran, hydroxypropyl-starch, chondroitin sulfate and hyalluronic acid; inclusive of derivatives thereof.
The surfactants are not particularly restricted but ionic and nonionic surfactants can be employed. Examples of the surfactants are polyoxyethylene glycol sorbitan alkyl esters, polyoxyethylene alkyl ethers, sorbitan monoacyl esters, and fatty acid glycerides.
The cellulose derivatives are not particularly restricted but include methylcellulose, ethylcellulose, hdroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose sodium and so on.
The carbohydrates can be used at least about 0.0001 mg, preferably within the range of about 0.01-10 mg per 1 xcexcg of the active ingredient. The surfactants can be used at least about 0.00001 mg, preferably within the range of about 0.0001-0.01 mg per 1 xcexcg of the active ingredient. The human serum albumin can be used at least about 0.0001 mg, preferably within the range of about 0.001-0.1 mg per 1 xcexcg of the active ingredient. The amino acids can be used within the range of about 0.001-10 mg per 1 xcexcg of the active ingredient. The cellulose derivatives can be used at least about 0.00001 mg, preferably within the range of about 0.001-0.1 mg per 1 xcexcg of the active ingredient.
The proportion of the active ingredient in the pharmaceutical preparation of the invention can be liberally selected from a broad range. Generally, the active ingredient accounts for the range of about 0.00001-70 weight %, preferably about 0.0001-5 weight % of the final preparation.
The buffer which may be optionally incorporated in the pharmaceutical preparation includes boric acid, phosphoric acid, acetic acid, citric acid, xcex5-aminocaproic acid, glutamic acid and the corresponding salts (e.g. salts with alkali metals or alkaline earth metals such as the sodium, potassium, calcium and magnesium salts). The isotonizing agent includes sodium chloride, potassium chloride, sugars and glycerine, among others. The chelating agent includes sodium edetate and citric acid.
The pharmaceutical preparation of the invention encompasses not only liquid preparations but also lyophilized preparations for extemporaneous reconstitution as prepared by freeze-drying liquid preparations for extended shelf lives. The lyophilized preparations are to be administered after dissolution in water or a buffer solution inclusive of physiological saline.
In molding the pharmaceutical composition of the invention into the tablet form, there can be used, as the carrier, various excipients such as lactose, sucrose, sodium chloride, glucose, urea, starch, calcium carbonate, kaolin, crystalline cellulose, silicic acid and potassium phosphate; binders such as water, ethanol, propanol, simple syrup, glucose solution, starch solution, gelatin solution, carboxymethyl cellulose, hydroxypropyl cellulose, methyl cellulose and polyvinyl pyrrolidone; disintegrators such as sodium carboxymethyl cellulose, calcium carboxymethyl cellulose, low-substituted hydroxypropyl cellulose, dry starch, sodium alginate, agar powder, laminaran powder, sodium hydrogen carbonate and calcium carbonate; surfactants such as polyoxyethylene sorbitan fatty acid ester, sodium lauryl sulfate and stearyl monoglyceride; disintegration inhibitors such as sucrose, stearin, cacao butter and hydrogenated oil; absorption promoters such as quaternary ammonium base and sodium lauryl sulfate, humectants such as glycerin and starch; adsorbents such as starch, lactose, kaolin, bentonite and colloidal silicic acid; and lubricants such as purified talc, stearic acid salt, boric acid powder and polyethylene glycol.
Furthermore, where necessary, the tablets obtained can be coated with the conventional coating materials to provide sugar-coated tablets, gelatin-coated tablets, enteric tablets, film-coated tablets or double- or multi-layer tablets.
The pills can be prepared using, as the carrier, excipients such as glucose, lactose, starch, cacao butter, hydrogenated vegetable oil, kaolin and talc; binders such as gum arabic powder, gum tragacanth powder, gelatin and ethanol, and disintegrators such as laminaran and agar.
Capsules are generally manufactured by formulating the active ingredient with a carrier or carriers such as those mentioned above by way of example and encapsulating the composition using hard gelatin or soft capsule shells, for instance.
The liquid preparation for oral administration includes solutions, emulsions, suspensions, syrup and elixirs. Each can be prepared using a conventional inert diluent, for example a pharmacologically acceptable vehicle inclusive of water. The liquid preparation may further be supplemented with various auxiliary agents such as a wetting agent, an emulsifier and/or a suspending agent and can be prepared by the established procedure.
The liquid preparation for parenteral administration, for example a sterile aqueous or nonaqueous solution, emulsion or suspension, can be prepared by using a diluent such as water, ethyl alcohol, propylene glycol, polyethylene glycol, ethoxylated isostearyl alcohol, polyoxylated isostearyl alcohol, polyethoxylated sorbitan fatty acid esters and vegetable oils such as olive oil. The liquid preparation may be supplemented with an organic ester which can be injected or infused, such as ethyl oleate. Such preparations may be further supplemented with the solubilizer, buffer, wetting agent, emulsifier, suspending agent, preservative, dispersant and other additives.
Such pharmaceutical preparations can be sterilized by filtration through a bacterial filter, incorporation of a bactericide, irradiation treatment, heat treatment, or the like. Moreover, such pharmaceutical preparations may each be provided in the form of a sterile solid composition, which can be dissolved in sterilized water or a suitable sterilizable medium for extemporaneous sterilization.
Rectal suppositories and vaginal preparations can be prepared by using polyethylene glycol, cacao butter, a higher alcohol, a higher alcohol ester, gelatin or a semi-synthetic glyceride as the carrier or base.
Ointments such as pastes, creams and gels can be prepared by using such a diluent or diluents as white petrolatum, paraffin, glycerin, cellulose derivatives, propylene glycol, polyethylene glycol, silicones, bentonite, and vegetable oils such as olive oil.
Pharmaceutical preparations for transnasal or sublingual administration can be prepared using the well-known standard excipient or excipients in the conventional manner.
Furthermore, where necessary, the pharmaceutical preparation of the invention can be supplemented with coloring agents, preservatives, perfumes, flavors, sweeteners or other pharmaceutical compositions.
The method for administration of said pharmaceutical preparation is not particularly restricted but can be judiciously selected with reference to the dosage form, patient background inclusive of age and sex, severity of illness, and other conditions. For example, the tablets, pills, solutions, suspensions, emulsions, granules and capsules are orally administered. The injections are intravenously administered either alone or in admixture with an ordinary infusion such as glucose and amino acid, and if necessary, administered alone intramuscularly, intradermally, subcutaneously or intraperitoneally. The suppositories are inserted into the rectum, while vaginal preparations are administered into the vagina. Transnasal preparations are administered into the nostrils, sublingualpreparations into the oral cavity, and ointments for transdermal absorption.
The amount of the active ingredient to be contained in said pharmaceutical preparation and the dosage are not particularly restricted but each can be judiciously selected from a broad range according to the expected therapeutic effect, method of administration, treatment time, patient factors such as age and sex. The dosage is usually selected so that the blood concentration of the active ingredient will be preferably about 1-200 xcexcg/ml, more preferably about 10-20 xcexcg/ml. This preparation can be administered once or in a few divided doses a day.
Production of a specific antibody against apM1 is now described in detail. The specific antibody against apM1 can be produced as an antiserum (polyclonal antibody) or a monoclonal antibody by utilizing apM1, a fragment thereof or a complex protein containing it as a hapten as an immunogen.
The technology for producing such antibodies are well understood by those skilled in the art. The antibody according to the invention can also be produced in accordance with the known method [e.g. Biochemical Experiments Series: xe2x80x9cMethods for Immunobiochemical Researchxe2x80x9d, Japanese Biochemical Society (ed.) (1986)].
More particularly, the monoclonal anti-apM1 antibody can be produced by, for example, a process which comprises constructing a fusion cell (hybridoma) between a plasmocyte (immunocyte) from a mammal immunized with said immunogen and a plasmacytoma cell of mammal origin, selecting a clone producing the desired apM1-recognizing antibody, and cultivating the clone.
The apM1 that can be used as an immunogen in the above procedure is not particularly restricted but may be any of the known recombinant apM1 species prepared by the recombinant DNA technology, a peptide having a partial amino acid sequence thereof, or the corresponding conjugated protein containing a prosthetic group. The apM1 mentioned above is known to be an adipose tissue-specific secretory factor and any protein having the equivalent activity or action, for example GBP 28 (gelatin-binding protein of 28 kDa), can also be used likewise as said immunogen.
The mammal to be immunized with said immunogen in the above procedure is not particularly restricted but is preferably selected from the standpoint of compatibility with the plasmacytoma cell to be used in cell fusion. Generally, the mouse, rat or rabbit is used with advantage.
The immunization of said mammal is carried out by the routine method, for example by injecting said immunogen by the intravenous, intradermal, subcutaneous, or intraperitoneal route. Preferably, the immunogen is administered alone or optionally in combination with an ordinary adjuvant to a laboratory animal, such as the mouse, several times at 2- to 14-day intervals, in a total dose of about 100-500 xcexcg/mouse. As the immunogen, it is preferable to use splenocytes isolated about 3 days after the last immunization.
As regards the mammalian plasmacytoma cell as the other parent cell to be fused with the immunocyte, any of the various cells already known, for example p3 (p3xc3x9763-Ag8) [Nature, 256, 495-497 (1975)], p3-U1 [Current Topics in Microbiology and Immunology, 81, 1-7 (1978)], NS-1 [Eur. J. Immunol., 6, 511-519 (1976)], MPC-11 [Cell, 8, 405-415 (1976)], SP2/0 [Nature, 276, 269-270 (1978)], FO [J. Immunol. Meth., 35, 1-21 (1980)],xc3x9763.6.5.3. [J. Immunol., 123, 1548-1550 (1979)], S194 [J. Exp. Med., 148, 313-323 (1978)], etc. and myeloma cells such as rat R210 [Nature, 277, 131-133 (1979)], can be employed.
The cell fusion reaction between said immunocyte and plasmacytoma cell can be carried out generally in accordance with the method of Milstein et al. [Methods in Enzymology, Vol. 73, p. 3 (1981)], for instance. More particularly, the above fusion reaction can be conducted in a usual medium in the presence of an ordinary fusion inducer, such as polyethylene glycol (PEG), Sendai virus (HVJ) or the like. To achieve an improved fusion efficiency, the medium may be optionally supplemented with an auxiliary agent such as dimethyl sulfoxide.
The ratio of the immunocyte to the plasmacytoma cell for use is not different from the ratio commonly used in this type of procedure. Thus, for example, the immunocyte is generally used in a proportion of about 1- to 10-fold as large as the amount of the plasmacytoma cell. Examples of the medium useful for the cell fusion are RPMI-1640 and MEM, which are generally used for proliferation of plasmacytoma cells, and other media which are used for cell culture of this kind. It is usually preferable that the serum component such as fetal calf serum (FCS) be omitted from the medium formulations.
Fusion is achieved by a procedure which comprises mixing predetermined amounts of said immunocyte and plasmacytoma cell thoroughly in said medium and adding a solution of PEG, for example a PEG with an average molecular weight of about 1000-6000, which has been prewarmed to about 37xc2x0 C., to the medium usually in a concentration of about 30-60 w/v %, followed by stirring. Thereafter, serial addition of a suitable medium, centrifugation and removal of the supernatant are repeated until the desired hybridoma has been obtained.
The hybridoma thus produced can be isolated by cultivating it in a usual selection medium, such as HAT (a medium containing hypoxanthine, aminopterin and thymidine). This culture using HAT medium is carried out for a sufficient time to kill the cells (unfused cells etc.) other than the desired hybridoma, usually for several days to a few weeks. The resulting hybridoma is subjected to a search for the clone producing the desired antibody by the usual limiting dilution method, followed by the production of monoclonal antibody.
The search for the desired antibody-producing clone can be carried out by the various methods in routine use for detection of antibodies, such as ELISA [Engvall, E., Meth. Enzymol., 70, 419-439 (1980)], plaque method, spot method, agglutination method, Ouchterlony method and radioimmunoassay (RIA) [Hybridoma Techniques and Monoclonal Antibodies, published by RandD Planning, K.K., pp. 30-53, Mar. 5, 1982]. The immunogen mentioned hereinbefore can be used for the purpose of this search.
The thus-obtained hybridoma producing the desired monoclonal antibody which recognizes apM1 can be subcultured in ordinary media and can also be stored for a long time in liquefied nitrogen.
Harvesting of the desired antibody from the above hybridoma can be effected by the method which comprises cultivating the hybridoma in the routine manner and harvesting the antibody as a culture supernatant or the method which comprises inoculating a compatible mammal with the hybridoma to cause it to multiply and harvesting the antibody as an ascites fluid. The former method is suitable for preparation of the antibody of high purity and the latter method is suitable for mass production of the antibody.
The antibody thus obtained can be purified by the conventional procedure such as precipitation, gel filtration, affinity chromatography, and so forth. In this manner, the desired anti-apM1 monoclonal antibody which specifically binds apM1 can be obtained.
The invention further provides a technique for the assay of apM1 in a sample and an associated method for diagnosis of arteriosclerosis.
The diagnosis of arteriosclerosis according to the invention comprises determining the amount of apM1 in a patient""s blood or urine sample with the anti-apM1 antibody by a liquid-phase or solid-phase immunoassay technique and comparing the measured value with the corresponding value in patients with arteriosclerosis and the corresponding value in healthy persons to see whether the apM1 level in the sample is higher or lower than the level in healthy persons.
The preferred immunoassay method is ELISA by the sandwich technique.
The above method is now described in detail. Its principle is based on the enzyme antibody method. Thus, this method typically comprises sowing an anti-human apM1 monoclonal antibody (the first antibody) on a 96-well plate and, to prevent nonspecific adsorption, carrying out blocking (immobilization). To this monoclonal antibody-immobilized plate, the human apM1 standard solution or the test sample is added and reacted (the first reaction). After the plate is washed, the anti-human apM1 antibody (the second antibody) is added and reacted (the second reaction). The plate is washed and the HRP-labeled anti-rabbit IgG antibody (the third antibody) is added and reacted (the third reaction). After the plate is washed, the substrate is added and the enzymatic reaction is carried out (the fourth reaction). Then, the activity is read as the absorbance at the wavelength of 492 nm.
In the above procedure, it is also possible to use the polyclonal antibody as the first antibody and the monoclonal antibody as the second antibody.
In the above method, the higher the concentration of apM1 in the standard solution or test sample used is, the higher is the enzyme activity (absorbance) detected. By constructing a standard curve (calibration curve) by plotting the absorbance values of standard solutions and comparing the absorbance of the test sample with the curve, the amount of apM1 in the test sample can be expediently found to diagnose whether the patient has arteriosclerosis or not.
Furthermore, the above diagnosis of arteriosclerosis according to this invention can be carried out more expediently by means of a kit and this invention further provides such a kit.
The kit of the invention and the method of detecting the amount of apM1 in a test sample are now described in detail.
In the assay procedure using the kit of the invention, the test sample is preferably a urine sample or a blood sample (particularly a serum or plasma sample from fasted blood), and such a sample can be obtained and prepared from the test subject in the routine manner.
The kit according to the invention comprises an anti-apM1 monoclonal or polyclonal antibody (anti-apM1 antibody) as an essential component, preferably a combination thereof with the anti-apM1 polyclonal antibody or monoclonal antibody, respectively, as the case may be, or a combination of said monoclonal antibodies.
The monoclonal antibody mentioned above is preferably used as immobilized by coupling it to a carrier on a plate in advance. As an alternative, said antibody can be directly used in an affinity gel form or used as the gel prepared in a vessel or test tube which can be shaken and centrifuged and lends itself to extraction of the non-affinity gel-bound fraction.
It is also preferable to equilibrate said antibody-immobilized plate or gel in advance with a suitable buffer solution, for example 0.01M Tris-HCl buffer (pH 7.4)+0.15M NaCl. Furthermore, said antibody-immobilized plate or gel may be supplemented with a usual preservative such as sodium azide.
More preferably, as an additional component of the kit of the invention, a labeled anti-human apM1 polyclonal antibody is supplied as the second antibody for ELISA. Where necessary, the kit of the invention may further comprise a stabilizer such as saccharose or bovine serum protein and/or a preservative. The preservative is selected from among substances which do not affect the test result with the kit and includes a diluted solution of sodium azide as a representative example.
Moreover, the kit of the invention may optionally comprise a water-soluble or -miscible substance such as glycerin, alcohol, glycol, glycoether or the like and, for degreasing purposes, a mixed organic solvent such as ethanol-diethyl ether, methanol-diethyl ether, or chloroform-methanol.